A spectrum is a basis of wireless communication. Spectrum resources include a licensed spectrum resource and an unlicensed spectrum resource. Currently, a main technology that uses the unlicensed spectrum resource is wireless fidelity (WiFi). However, the WiFi has disadvantages in terms of mobility, security, quality of service (QoS), and concurrent processing of multi-user scheduling. Therefore, applying an unlicensed spectrum to a Long Term Evolution (LTE) device can not only result in effective use of the unlicensed spectrum resource, but also provide more effective wireless access and meet a growing demand for mobile broadband service. Therefore, in a future mobile communications scenario, both an LTE base station device and a WiFi device exist on the unlicensed spectrum. One of feasible solutions of using the unlicensed spectrum by the LTE base station is that the unlicensed spectrum is used as a secondary cell (Scell) of LTE user equipment (UE) and is configured for the UE, so that the LTE base station can perform data communication with the UE by using the unlicensed spectrum.
In an LTE system and in an LTE Advanced (LTE-A) system, a random access procedure is required when data transmission is performed for using a licensed spectrum. Random access procedures are classified into a non-contention based random access procedure and a contention-based random access procedure. Random access parameters used in a random access procedure of the prior art, such as a physical random access channel resource and a parameter related to random access, are notified to UE mainly by using system broadcast information; for example, information such as a subframe or frequency channel number with the physical random access channel (PRACH) resource, a random access code set, a random access code group, a maximum quantity of sending times of a random access code, and a size of a random access response message receiving window is notified to the UE. When the UE executes a contention-based random access procedure, the UE selects a random access code according to the random access parameters in the system message, and sends the selected random access code on a selected random access channel. When the UE executes a non-contention based random access procedure, the UE determines the random access channel based on the random access parameters in the system message and a random access channel mask sequence number notified by a base station by using a physical downlink control channel (PDCCH) command, and sends, on the determined random access channel, the random access code notified by using the PDCCH command to the base station. After sending the random access code, the UE receives a random access response message in the random access response message receiving window in the random access parameters notified by the base station by using the system broadcast message.
Currently, a random access procedure is also required when data transmission is performed for using an unlicensed spectrum. However, because a contention and a collision may exist on an unlicensed spectrum resource, that is, the unlicensed spectrum resource may be sometimes available or sometimes unavailable. Therefore, if a PRACH resource on the unlicensed spectrum is also notified by using system broadcast information, it may occur that a subframe of the configured PRACH resource is unavailable, while an available subframe is not provided with the PRACH resource, and consequently the random access procedure cannot be executed on the unlicensed spectrum.